Whats an alternative way of updating a page with new records as they are inserted into a table automatically without using jquery/ajax

I've wrote a small chat system using jquery, php, and mysql; however, I'm looking for some kind of technology that will only update a if a new record is inserted into a row. I feel like using jquer开发者_JAVA技巧y ajax calls every second to retrieve new records is really overkill and strenuous on my server.

You are looking for a Comet solution: http://en.wikipedia.org/wiki/Comet_%28programming%29

The idea, as pdr noted, is to the javascript continuously open an async request with the server. The server holds it open, but does not send anything until it determines there is something to send. The request will timeout on the javascript side after 10-20 seconds, after which it should re-open the connection.

This uses a 'subscriber' based model, by which the server will send out the chat message or what have you, to all clients which are subscribed, all at once. This saves you many database requests, as the server is the one asking for the requests, not the individual clients.

What you want is long polling. Basically, you make an XHR, and the server and PHP holdes the request open until new data is ready to be sent back.

You need to configure Apache not to timeout in this circumstances, so do some substantial research. Basically, the PHP looks like so...

set_time_limit(0);

while (TRUE) {

   $db->query('SELECT `message` FROM `messages` WHERE `new` = TRUE');

   if ($db) {
       echo json_encode($db->results());
       exit;
   }
   sleep(1);
}

Then, you make an XHR for this page, and it will stay open until new data is ready. Then, on the complete callback, update your page's state and make a new XHR.

This is a lot more efficient than polling for updates continually using XHR.

Make sure you do a lot of research because I believe Apache is going to think things are wrong if a PHP script hasn't stopped after 30 seconds or so. :)

There are a couple routes I know of that you can take.

1. Long polling. This is where the browser opens a connection to the server and does nothing until the server responds. Once the server responds or times-out (sends an empty response to the browser), a new long-polling request is made.

   When going this route, you should use a server that does not rely on using a new thread for each request.

2. Web sockets. Again, you'll want a server that can handle requests without spawning a new thread every request. With web sockets, a connection is kept open between the client and servier, and unlike Long polling, doesn't time out. However, this isn't well-supported yet.

I highly recommend checking out http://socket.io/

The point of Ajax is that it's asynchronous. Can you not just wait at the server until there's a worthwhile response to send?

With standard HTML/CSS/JS, that's pretty much the only way since the browser can make requests of the server, not vice versa. The AJAX call shouldn't have to be very big at all. A chat system, by definition, is going to require hitting the server a lot.